Palladium-containing catalysts, particularly heterogeneous catalysts wherein the palladium is supported on carbon, alumina, or the like, have been used as the catalyst in a number of chemical processes, especially processes involving the conversion of hydrocarbons at a temperature below about 400.degree. C.
Recently, such a catalyst has been found to be highly active and selective for the dehydrogenation of dimethyltetrahydronaphthalenes to dimethylnaphthalenes under liquid phase elevated temperature conditions. However, in such a process, the catalyst activity unfortunately declines significantly after several uses.
Normal regeneration procedures for fixed bed catalysts, such as supported heterogeneous catalysts, call for elevated temperature heating to remove the deactivating species by oxidation. However, palladium is known to sinter at the elevated temperatures typically used for such a heating which are about 400.degree. to about 500.degree. C. Thus, such a heating results in permanent damage to the catalyst and resultant reduced catalytic activity.
A palladium-containing catalyst is expensive. When it is deactivated, it is typically returned to the manufacturer to recover the palladium, which is also an expensive process. The art of redispersing palladium on a heat-treated supported palladium catalyst has not been developed.
Thus, problems with deactivation in use and in reactivation tend to retard the usability and acceptance for commercial purposes of palladium containing catalysts.
A new and improved method for regenerating a deactivated palladium containing catalyst would be desirable. The present invention provides such a method.